1. Field of the Invention
The field of art to which the claimed invention pertains is hydrocarbon separation. More specifically, the claimed invention relates to the separation of a monoaromatic hydrocarbon using a solid adsorbent which selectively removes one or more of the aromatic components from the feed stock.
2.
Description of the Prior Art
It is known in the separation art that certain crystalline aluminosilicates can be used to separate individual hydrocarbons from mixtures thereof. In particular, the separation of normal paraffins from branched chained paraffins can be accomplished by using the Type A zeolites which have pore openings from 3 to about 5 Angstroms. These adsorbents allow a separation based on the physical size differences in the molecules by allowing the smaller or normal hydrocarbons to be passed into the cavities within the crystalline aluminosilicate adsorbent, while excluding the larger or branched chain molecules. Other separations have been recognized using the larger pore diameter zeolites -- namely, the type X or type Y structured zeolites to separate xylene isomers or the polynuclear aromatics such as the alkyl substituted naphthalenes.
The present invention relates to the separation of mono-nuclear aromatic hydrocarbons having more than eight carbons atoms per molecule and necessarily exclude the teachings specifically directed towards xylene separation.
We have found that type X and type Y structured crystalline aluminosilicate zeolites which contain certain selected cations provide selectivities which preferably allow one or more isomer from a group of isomers to be adsorbed by the adsorbent.